U.S. patent number 7,625,102 [Application Number 11/248,142] was granted by the patent office on 2009-12-01 for lighting device.
This patent grant is currently assigned to Stanley Electric Co., Ltd.. Invention is credited to Shoichi Bamba, Teruo Koike, Ryotaro Owada.
United States Patent |
7,625,102 |
Koike , et al. |
December 1, 2009 |
Lighting device
Abstract
A lighting device can have a simple configuration which can be
formed compactly in the direction of its optical axis in
particular, and with a light weight. The lighting device can also
have a functional, three-dimensional innovative appearance for the
sake of enhanced merchantability and novelty. The lighting device
can include a light source and a projection lens which is situated
so that its source-side focus lies near the light source and its
optical axis generally coincides with that of the light source. The
projection lens can be a distribution control lens of convex form,
having an exit surface shaped aspherically so that the direction of
emission is continuously refracted into specified directions with
respect to the angle of incidence from the focal position.
Inventors: |
Koike; Teruo (Tokyo,
JP), Bamba; Shoichi (Tokyo, JP), Owada;
Ryotaro (Tokyo, JP) |
Assignee: |
Stanley Electric Co., Ltd.
(Tokyo, JP)
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Family
ID: |
36180530 |
Appl.
No.: |
11/248,142 |
Filed: |
October 13, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060083002 A1 |
Apr 20, 2006 |
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Foreign Application Priority Data
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Oct 14, 2004 [JP] |
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2004-300655 |
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Current U.S.
Class: |
362/277; 362/335;
362/311.1; 359/728; 359/708 |
Current CPC
Class: |
F21S
41/28 (20180101); F21V 5/04 (20130101); F21S
41/151 (20180101); F21S 43/40 (20180101); F21S
41/147 (20180101); F21S 43/26 (20180101); F21S
41/143 (20180101); F21V 13/04 (20130101); F21Y
2115/10 (20160801); F21W 2131/103 (20130101) |
Current International
Class: |
G02B
3/02 (20060101) |
Field of
Search: |
;362/326,277,327,328,335,336,347,538 ;359/708,728 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: O'Shea; Sandra L
Assistant Examiner: Dzierzynski; Evan
Attorney, Agent or Firm: Cermak Knealy Vaidya & Nakajima
LLP
Claims
What is claimed is:
1. A lighting device comprising: at least one light source having
an optical axis; and a projection lens having an optical axis and a
source-side focal position, the projection lens located adjacent
said light source so that the source-side focal position is located
substantially at said light source and the optical axis of the
projection lens substantially coincides with the optical axis of
said light source, said projection lens being a distribution
control lens of convex form having an exit surface that is
aspherically shaped so that a direction of emission light is
continuously refracted into a certain direction with respect to an
angle of incidence .theta.1 of light originating from the focal
position, the aspherically shaped exit surface of the distribution
control lens including a concave surface portion located between a
first convex surface and a second convex surface, the optical axis
of the projection lens intersecting the concave surface portion;
wherein the aspherically shaped exit surface of the distribution
control lens is configured such that an angle of emission .theta.2
is related to the angle of incidence .theta.1 in accordance with
the formula .theta.2=0.2.theta.1.
2. The lighting device according to claim 1, wherein said
projection lens functions as a convex lens in a first direction
perpendicular to the optical axis, and emits light diffused in a
second direction perpendicular to both the optical axis and the
first direction.
3. The lighting device according to claim 2, wherein said
projection lens refracts the light in the second direction so that
an angle of emission of the emitted light has a predetermined ratio
to an angle of incidence of the light originating from the focal
position.
4. The lighting device according to claim 3, wherein said light
source is a light emitting semiconductor device.
5. The lighting device according to claim 4, wherein said light
source is a light emitting diode.
6. The lighting device according to claim 2, wherein said light
source is a light emitting semiconductor device.
7. The lighting device according to claim 6, wherein said light
source is a light emitting diode.
8. The lighting device according to claim 1, wherein the certain
direction extends away from the optical axis of the projection lens
and substantially all of the light emitted by the light source and
incident on the projection lens is diffused in the certain
direction.
9. The lighting device according to claim 1, wherein substantially
all of the light emitted by the light source is directly incident
on the projection lens, and the emission light is diffused by the
projection lens in a first direction and in the certain direction,
where the first direction is substantially perpendicular to the
optical axis of the projection lens, the certain direction is
substantially perpendicular to the first direction, and wherein a
distance of the emission light diffused in the certain direction is
substantially greater than a distance of the emission light
diffused in the first direction.
10. The lighting device according to claim 9, wherein a ratio of
the distance of the emission light diffused in the first direction
to the distance of the emission light diffused in the certain
direction is approximately 4:20.
11. A lighting device comprising: at least one light source having
an optical axis; a reflecting member located adjacent said light
source, the reflecting member having a reflecting surface that has
a first focal position, a second focal position, and a major axis,
the reflecting surface being situated so that the first focal
position of the reflecting surface is located substantially at said
light source and the major axis of the reflecting surface
substantially coincides with the optical axis of said light source;
and a projection lens having an optical axis and a focus, the
projection lens situated so that the focus of the projection lens
is located substantially at the second focal position of said
reflecting surface, and the optical axis of the projection lens
substantially coincides with the major axis of said reflecting
surface, said projection lens being a distribution control lens of
convex form having an exit surface that is aspherically shaped so
that a direction of emission light is continuously refracted into a
certain direction with respect to an angle of incidence .theta.1 of
light originating from the second focal position, wherein the light
source is a light emitting semiconductor device, the aspherically
shaped exit surface of the distribution control lens including a
concave surface portion located between a first convex surface
portion and a second convex surface portion, the optical axis of
the projection lens intersecting the concave surface portion;
wherein the aspherically shaped exit surface of the distribution
control lens is configured such that an angle of emission .theta.2
is related to the angle of incidence .theta.1 in accordance with
the formula .theta.2=0.2.theta.1.
12. The lighting device according to claim 11, wherein said
reflecting member is arranged only in an area forward of said light
source.
13. The lighting device according to claim 12, wherein said light
source is a light emitting diode.
14. The lighting device according to claim 11, wherein said
projection lens functions as a convex lens in a first direction
perpendicular to the optical axis, and emits light diffused in a
second direction perpendicular to both the optical axis and the
first direction.
15. The lighting device according to claim 14, wherein said
projection lens refracts the light in the second direction so that
an angle of emission of the emitted light has a predetermined ratio
to an angle of incidence of the light originating from the second
focal position.
16. The lighting device according to claim 11, wherein said light
source is a light emitting diode.
17. The lighting device according to claim 11, wherein said
reflecting member has a mounting part configured to fix and hold
said projection lens.
18. The lighting device according to claim 11, wherein the
reflecting surface is an elliptic reflecting surface.
19. The lighting device according to claim 11, wherein the certain
direction extends away from the optical axis of the projection lens
and substantially all of the light emitted by the light source and
incident on the projection lens is diffused in the certain
direction.
20. The lighting device according to claim 11, wherein the emission
light is diffused by the projection lens to a first extent measured
in a first direction and to a second extent measured in the certain
direction, where the first direction is substantially perpendicular
to the optical axis of the projection lens, the certain direction
is substantially perpendicular to the first direction, and the
second extent is substantially greater than the first extent.
21. The lighting device according to claim 20, wherein a ratio of
the distance of the emission light diffused in the first direction
to the distance of the emission light diffused in the certain
direction is approximately 4:20.
22. A lighting device comprising: at least one light source having
an optical axis; and a projection lens having an optical axis and a
source-side focal position, the projection lens located adjacent
said light source so that the source-side focal position is located
substantially at said light source and the optical axis of the
projection lens substantially coincides with the optical axis of
said light source, said projection lens being a distribution
control lens of convex form having an exit surface that is
aspherically shaped so that a direction of emission light is
continuously refracted into a certain direction with respect to an
angle of incidence .theta.1 of light originating from the focal
position, wherein said light source is a light emitting
semiconductor device, the projection lens having an outer perimeter
configured such that the projection lens is non-circular when
viewed from along the optical axis of the projection lens; wherein
the aspherically shaped exit surface of the distribution control
lens is configured such that an angle of emission .theta.2 is
related to the angle of incidence .theta.1 in accordance with the
formula .theta.2=0.2.theta.1.
23. The lighting device according to claim 22, wherein said light
source is a light emitting diode.
24. The lighting device according to claim 22, wherein the
aspherically shaped exit surface of the distribution control lens
includes a concave surface portion located between a first convex
surface and a second convex surface, the optical axis of the
projection lens intersecting the concave surface portion.
Description
This application claims the priority benefit under 35 U.S.C.
.sctn.119 of Japanese Patent Application No. 2004-300655 filed on
Oct. 14, 2004, which is hereby incorporated in its entirety by
reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a lighting device, and more particularly
to automotive/vehicular lighting devices such as headlamps,
auxiliary headlamps, and various lamps that are arranged in front
parts of a motor vehicle. In addition, the invention relates to
illuminating lights for use in lighting fixtures such as traffic
lamps, household lamps, general vehicle lamps, etc.
2. Description of the Related Art
FIGS. 1 and 2 show examples of configurations of conventional
lighting devices. The lighting device 1 shown in FIG. 1 is composed
of a light source 2, a projection lens 3 for focusing the light
from the light source 2, and a distribution control member 4
arranged in front of the projection lens 3.
The light source 2 is a near point-like light source, such as an
LED. When a drive voltage is applied thereto, the LED emits light
to a predetermined range of angles about its optical axis
perpendicular to a mounting board 2a.
The projection lens 3 is made of a convex lens. This convex lens is
configured so that its source-side focus lies near the light source
2, and its optical axis coincides with that of the light source
2.
The distribution control member 4 is a plate-like transparent
member, for example, which has lens-cut prisms for light diffusion
on one of its surfaces (in the case shown in FIG. 1, the lens-cut
prisms are provided on the source-side bottom surface).
In the lighting device 1 thus configured, light emitted from the
light source 2 is incident on the projection lens 3. The light is
focused by the projection lens 3 into near parallel light, which is
incident on the distribution control member 4. The light incident
on the distribution control member 4 is then diffused by the
distribution control member 4 as appropriate, given a desired light
distribution characteristic, and is projected toward the front.
Turning now to FIG. 2, a lighting device 5 is composed of a light
source 2, a reflecting surface 6 for reflecting light from the
light source 2 toward the front (upward in the diagram), and a
projection lens 7 for focusing the light from the reflecting
surface 6.
The reflecting surface 6 is made of an elliptic reflecting surface,
for example, which is situated so that a first focus thereof lies
near the light source 2 and its major axis coincides with the
optical axis of the light source 2. The projection lens 7 is made
of an aspheric lens. This aspheric lens is situated so that its
source-side focus lies near a second focus of the reflecting
surface 6 and its optical axis coincides with that of the light
source 2.
In the lighting device 5 thus configured, the light emitted from
the light source 2 is reflected by the reflecting surface 6 and
incident on the projection lens 7. Then, the light is focused by
the projection lens 7 as well as controlled in distribution based
on the aspheric configuration of the same. As a result, the light
is projected toward the front with a predetermined light
distribution characteristic.
The foregoing lighting devices 1 and 5, however, have had the
following problems.
That is, in the lighting device 1, obtaining a desired light
distribution characteristic requires the two optical members, i.e.,
the projection lens 3 and the distribution control member 4. The
light transmittances of these optical members thus have an effect
on this optical system, increasing the transmission loss of the
light. These optical members can cause additional problems in
accuracies, such as a positional accuracy and a tilt accuracy with
each other. In addition, the large dimension in the direction of
the optical axis also produces the problem of an increase in total
weight.
With the lighting device 5, the use of the reflecting surface 6 can
make the light transmission loss smaller than in the lighting
device 1. Nevertheless, since the reflecting surface 6 is arranged
behind the light source 2, there have also been problems in that
the device requires a large dimension in the direction of the
optical axis and has an increased total weight.
Furthermore, the lighting devices 1 and 5 are both round in
appearance. This leads to stereotypical designs with fewer
variations in appearance. Since it is difficult and sometimes
impossible to provide functional three-dimensional appearances,
there have been problems with poor merchantability and design
novelty.
SUMMARY OF THE INVENTION
In view of the foregoing and other problems, desires and needs, an
aspect of the invention includes a lighting device that has a
simple configuration which can be formed compactly in the direction
of its optical axis, that has a comparatively light weight, and
that has a functional three-dimensional appearance of innovative
design for the sake of enhanced merchantability and novelty.
Another aspect of the invention includes providing a lighting
device that can include at least one light source and a projection
lens arranged corresponding to the light source so that a
source-side focal position thereof lies near the light source and
an optical axis thereof generally coincides with an optical axis of
the light source. In this configuration, the projection lens is a
distribution control lens of convex form having an exit surface
shaped aspherically so that the direction of emission is
continuously refracted into a certain direction with respect to the
angle of incidence from the focal position.
A second aspect of the present invention includes providing a
lighting device that can include at least one light source, a
reflecting member arranged corresponding to the light source and
having an elliptic reflecting surface situated so that a first
focal position thereof lies near the light source and a major axis
thereof coincides with an optical axis of the light source, and a
projection lens situated so that a focus thereof lies near a second
focal position of the reflecting surface and an optical axis
thereof generally coincides with the major axis of the reflecting
surface. In this configuration, the projection lens is a
distribution control lens of convex form having an exit surface
shaped aspherically so that the direction of emission is
continuously refracted into a certain direction with respect to the
angle of incidence from the second focal position.
In the lighting devices described above, the reflecting member may
be arranged only in the area forward of the light source.
In the lighting devices described above, the projection lens may
function as a convex lens in a first direction perpendicular to the
optical axis, and emit light diffused in a second direction
perpendicular to both the optical axis and the first direction.
In the lighting devices described above, the projection lens may
refract the light in the second direction so that the angle of
emission has a predetermined ratio to the angle of incidence.
Furthermore, in the lighting devices described above, the light
source may be a light emitting device, and in particular, a light
emitting diode.
In the lighting devices described above, the reflecting member may
have a mounting part for fixing and holding the projection
lens.
According to the foregoing first aspect, when light emitted from
the light source is incident on the corresponding projection lens,
it is focused by the projection lens and projected toward the
front. On this occasion, the light incident on the projection lens
from the light source is refracted so that the direction of
emission is changed into a certain direction with respect to the
angle of incidence based on the shape of the exit surface of the
projection lens. This achieves a light distribution control. Here,
the shape of the exit surface of the projection lens can be
controlled to easily realize an arbitrary and/or predetermined
light distribution characteristic.
According to this aspect of the invention, the projection lens may
have a distribution control function. No more than one optical
member may be necessary to transmit the light from the light
source. In other words, as compared to the case where the
projection lens is accompanied with an additional distribution
control member, it is possible to reduce the transmission loss,
reduce the size in the direction of the optical axis, and achieve
weight saving.
Furthermore, in the foregoing aspect, the exit surface of the
projection lens is not necessarily formed to be rotationally
symmetrical about the optical axis. The projection lens, as viewed
from the front, thus may have a rim of rotationally asymmetric
shape, and not a perfectly circular one. This allows innovative
designs for enhanced merchantability and novelty.
According to the foregoing second aspect, the light emitted from
the light source is incident on the reflecting surface of the
corresponding reflecting member, and reflected from this reflecting
surface toward the second focal position. Then, the light is
focused by the projection lens, and projected toward the front.
Here, the light that is reflected by the reflecting surface of the
reflecting member and incident on the projection lens is refracted
so that the direction of emission is changed into a certain
direction with respect to the angle of incidence based on the shape
of the exit surface of the projection lens. This achieves a light
distribution control.
As is the case with the lighting device according to the first
aspect, it is then possible to realize an arbitrary and/or
predetermined light distribution characteristic. In addition, the
projection lens has a distribution control fiction. It may
therefore be possible to reduce the transmission loss, reduce the
size in the direction of the optical axis, and achieve weight
saving. This also allows innovative designs for enhanced
merchantability and novelty.
In the foregoing aspect, the reflecting member can be arranged only
in an area forward of the light source. Here, the reflecting member
has no protrusion behind the light source. This allows a further
reduction of the dimension in the direction of the optical
axis.
The projection lens may function as a convex lens in a first
direction perpendicular to the optical axis, and may emit light
diffused in a second direction perpendicular to both the optical
axis and the first direction. In this case, it is possible to
obtain a light distribution characteristic of a flat projection
pattern, diffused in the second direction.
The projection lens refracts the light in the second direction so
that the angle of emission has a predetermined ratio to the angle
of incidence. This also makes it possible to obtain a light
distribution characteristic of a flat projection pattern, diffused
in the second direction.
The light source can be a light emitting device, such as an LED. In
this case, the light emitted from the light source, or the light
emitting device or LED in particular, is given the light
distribution characteristic controlled by the projection lens and
is projected toward the front.
The reflecting member can have a mounting part such as an indent, a
mounting surface, a separate attachment structure, etc., attached
to or built into the reflecting member for fixing and holding the
projection lens. In this case, the reflecting member and the
projection lens can be accurately and easily positioned with
respect to each other.
As described above, the exit surface of the projection lens can be
given a surface configuration having a distribution control
function. This eliminates the need for conventional separate
distribution control members. The optical system thus allows a
reduction in the transmission loss of the light from the light
source. The optical system can also be configured compactly in the
direction of the optical axis, with a lighter weight on the whole.
Moreover, the projection lens, as viewed from the front, does not
necessarily have a rim of perfectly circular shape, but can have
other shapes, such as an elliptic or other odd-shape. This allows
innovative designs for enhanced merchantability and novelty.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other characteristics, benefits and advantages of the
invention will become clear from the following description with
reference to the accompanying drawings, wherein:
FIG. 1 is a schematic sectional view showing the configuration of
an example of a conventional lighting device;
FIG. 2 is a schematic sectional view showing the configuration of
another example of a conventional lighting device;
FIG. 3 is a schematic sectional view showing the configuration of a
first exemplary embodiment of a lighting device made in accordance
with principles of the invention;
FIG. 4 is a schematic perspective view showing a projection lens of
the lighting device of FIG. 3;
FIG. 5 is a graph showing light distribution characteristics of the
lighting device of FIG. 3;
FIG. 6 is a schematic diagram showing a design example of the
projection lens for the lighting device of FIG. 3;
FIGS. 7A and 7B are graphs showing light distribution
characteristics of an ordinary convex lens and that of the
projection lens according to the design example of FIG. 6;
FIG. 8 is a schematic sectional view showing the configuration of
another exemplary embodiment of a lighting device made in
accordance with principles of the invention;
FIG. 9 is a schematic perspective view showing the reflecting
member of the lighting device of FIG. 8;
FIG. 10 is a schematic sectional view showing the configuration of
another exemplary embodiment of a lighting device made in
accordance with principles of the invention;
FIG. 11 is a schematic perspective view showing a lighting device
unit in the lighting device of FIG. 10;
FIG. 12 is a schematic perspective view showing a housing of the
lighting device of FIG. 10; and
FIG. 13 is a graph showing light distribution characteristics of
the lighting device of FIG. 10.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Hereinafter, exemplary embodiments of the invention will be
described in detail with reference to FIGS. 3 to 13.
Incidentally, the following embodiments are concrete examples of
the invention, and thus include various features that are
technically beneficial and/or operable. Nevertheless, the scope of
the invention shall not be limited to these aspects.
FIG. 3 shows the configuration of a lighting device according to an
exemplary embodiment of the invention.
In FIG. 3, the lighting device 10 can include a light source, or a
bulb 11, and a projection lens 12 which lies in front of the bulb
11 and focuses light from the bulb 11.
For example, the bulb 11 may be an incandescent bulb, a halogen
lamp, a halogen lamp with an infrared reflecting film, a discharge
lamp such as a metal halide lamp, or other light source. The bulb
11 can be fixed, held, and fed by a socket. Incidentally, the
lighting device may use an LED for its light source, instead of the
bulb 11.
The projection lens 12 can be generally convex in shape, and placed
on the optical axis extending in front of the bulb 11. The
projection lens 12 focuses the light from the bulb 11 and projects
it toward the front. Here, the projection lens 12 can be situated
so that its focus F on the side of the bulb 11 lies near the bulb
11.
As shown in FIG. 4, the projection lens 12 has an exit surface, or
a front surface 12a, that is formed as a distribution control lens.
The distribution control will be described in more detail
below.
The exit surface 12a of the projection lens 12 can be formed into
an aspheric shape, so that light incident from the focal position F
is emitted so that the direction of emission is continuously
refracted into specified directions with respect to the angle of
incidence.
FIG. 5 shows simulated light distribution characteristics for the
projection lens 12.
In the present exemplary embodiment, the projection lens 12 is
designed on the basis of a convex lens. In particular, given an
angle of incidence .theta.1 of light, the angle of emission
.theta.2 can be calculated uniquely based on the angle of incidence
.theta.1 (and such constants as the backside configuration and the
refractivity of the projection lens 12).
The projection lens 12 is configured to function as a convex lens
and emit parallel light in a first direction x perpendicular to its
optical axis. The projection lens 12 is also configured, for
example, so that it provides the angle of emission
.theta.2=0.2.theta.1 with respect to the angle of incidence
.theta.1 as far as a second direction y perpendicular to the first
direction x is concerned. FIG. 6 shows how incident light is
diffused here.
Consequently, as compared to the light distribution characteristic
of an ordinary convex lens (see FIG. 7A), the projection lens 12
can have light distribution characteristics as shown in FIG. 7B.
That is, the projection lens 12 functions as a so-called horizontal
diffusion lens which diffuses incident light in the second
direction.
Incidentally, a projection lens 12 like this can be designed, for
example, by using lens design techniques disclosed in Japanese
Patent Laid-Open Publication No. 2004-087179, which disclosure is
incorporated herein in its entirety by reference. For example, it
can be designed easily by determining the position of the exit
surface based on the direction of emission with respect to the
angle of incidence .theta.1 in units of small angles.
The projection lens 12 can thus be given the foregoing light
distribution characteristic shown in FIG. 5 by appropriately
determining the surface configuration of the front surface 12a.
In the lighting device 10 thus configured, the bulb 11 is fed from
the socket for light emission. Here, the light L emitted from the
emission center of the bulb 11 is incident on the projection lens
12, and is focused and projected toward the front by the projection
lens 12.
In this case, the front surface 12a or the exit surface of the
projection lens 12 can have a distribution control function, being
shaped to the surface configuration mentioned above. This
eliminates the need for conventional distribution control members,
thereby allowing a reduction in parts count and a lighter weight on
the whole. In addition, the light from the light source, or the
bulb 11, is transmitted through the projection lens 12 alone before
being projected toward the front. The light transmission loss in
the optical system can thus be reduced.
Moreover, when the projection lens 12 is viewed from the front, the
rim of the projection lens 12 is not necessarily a perfect circle
in shape. This allows for novel designs.
FIG. 8 shows the configuration of a lighting device according to
another exemplary embodiment of the invention.
In FIG. 8, the lighting device 20 includes a bulb 21, a reflecting
member 22, and a projection lens 23. The bulb 21 serves as a light
source. The reflecting member 22 is arranged so as to surround the
bulb 21 and has a reflecting surface 22a for reflecting the light
from the bulb 21 toward the front. The projection lens 23 lies in
front of the bulb 21, and focuses the light from the bulb 21 and
the reflecting surface 22a. The bulb 21 may have the same
configuration as that of the bulb 11 described above. It can thus
be fixed, held, and fed by a socket. Incidentally, the lighting
device here may use an LED for its light source, instead of the
bulb 21.
The reflecting member 22 can be made of plastic, for example, and
can have a reflecting surface 22a which opens to the top as shown
in FIG. 9. A reflecting film or reflective coating is formed over
this reflecting surface 22a, for example.
This reflecting surface 22a may be formed only in an area forward
of a mounting board 21a of the bulb 21. It reflects the light from
the bulb 21 toward the front, introducing it to the projection lens
23. For example, this reflecting surface 22a may be formed as an
elliptic reflecting surface that sinks away from the front.
Here, the elliptic reflecting surface may be a free-form surface
based on a spheroidal or ellipsoidal surface.
The reflecting surface 22a is then situated so that a first focus
F1 thereof lies near the bulb 21 and its major axis is along the
optical axis of the bulb 21.
The top of the reflecting member 22 is formed as a mounting surface
22b intended for the projection lens 23. The projection lens 23 is
placed on this mounting surface 22b of the reflecting member 22,
and fixed by screws, adhesive or the like. The projection lens 23
can thus be accurately and easily positioned with respect to the
reflecting member 22.
The projection lens 23 can have the same convex shape as that of
the projection lens 12, and can be placed on the optical axis
extending in front of the bulb 21. The projection lens 23 focuses
the light coming directly from the bulb 21 and the light reflected
from the reflecting surface 22a, and projects the resultant light
toward the front.
Here, the projection lens 23 is situated so that its focus on the
side of the bulb 21 lies near the first focus F1 of the reflecting
surface 22a.
In the lighting device 20 thus configured, the bulb 21 is fed from
the socket for light emission. Here, the light L emitted from the
emission center of the bulb 21 is incident on the projection lens
22 directly or after being reflected from the reflecting surface
22a of the reflecting member 22. The light L is then focused and
projected toward the front by the projection lens 23.
In this case, the front surface, or exit surface, of the projection
lens 23 has a distribution control function. This eliminates the
need for conventional distribution control members, thereby
allowing a reduction in parts count and a lighter weight on the
whole. In addition, the light from the light source, or the bulb
21, can be transmitted through the projection lens 23 alone before
being projected toward the front. Light transmission loss in the
optical system can thus be reduced.
Since the reflecting surface 22a of the reflecting member 22 may be
formed only in the area forward of the bulb 21, the entire lighting
device 20 can be configured compactly in the direction of the
optical axis.
In addition, when the projection lens 23 is viewed from the front,
the rim of the projection lens 23 is not necessarily a perfect
circle in shape. This allows for novel designs.
FIG. 10 shows the configuration of a lighting device according to
another exemplary embodiment of the invention.
In FIG. 10, the lighting device 30 is formed as a lighting fixture
including a plurality of lighting devices 10 as shown in FIG.
3.
In the lighting device 30, the lighting devices 10 are grouped by
threes to form lighting device units 31 as shown in FIG. 11. Each
of the lighting device units 31 has three lighting devices 10 which
are fixed and held in the same direction. The lighting devices 10
may use LEDs for their respective light sources, instead of the
bulbs 11. Here, the lighting devices 10 are each configured to have
a light distribution characteristic intended for a relatively
narrow coverage.
The present exemplary embodiment includes twenty-four (24) lighting
device units 31 in total, each of which is fixed in a predetermined
orientation with respect to a housing 32. Consequently, the
lighting device units 31 irradiate 24 sections of projection area
with light, respectively.
Consequently, the lighting device 30 as a whole has a light
distribution characteristic that includes a relatively wide
coverage.
As shown in FIG. 12, the housing 32 has heat sinks 32a for
radiating heat generated by the lighting device units 31 on its
outside.
According to the lighting device 30 thus configured, each of the
lighting devices 10 constituting the lighting device units 31 can
operate in a similar manner as compared to operation of the
lighting device 10 shown in FIG. 3. The lighting device 30 thus
offers a wide range of light illumination on the whole. In
addition, the front surfaces 12a of the projection lenses 12 in the
respective lighting devices 10 can be selectively shaped in
accordance with appropriately-selected surface configurations, so
that a uniform light distribution characteristic can be obtained on
the whole. FIG. 13 shows a simulated light distribution
characteristic for the lighting device of this configuration.
In using light sources of relatively low light intensities, such as
LEDs, a plurality of lighting devices 10 can be combined to form a
lighting device unit 31. Here, it is possible to achieve a desired
light distribution characteristic by irradiating relatively narrow
ranges of illumination with required intensities of light from the
so-called multiple light sources.
As described above, the front surfaces of the projection lenses 12
and 23 can have a distribution control function. This eliminates
the need for additional distribution control members.
As a result, the entirety of the lighting devices can be configured
compactly in the direction of the optical axis and can achieve
comparatively lighter weights. In addition, the projection lenses
12 and 23, as viewed from the front, have rims that can be shaped
differently from a perfect circle. This allows for innovative
designs for enhanced merchantability and novelty.
Consequently, it is possible to provide optimum lighting devices
for various purposes, including automotive lighting devices such as
headlamps, auxiliary headlamps, and signal lamps, as well as
traffic sign lamps, traffic signals, general lighting, working
lamps, general indicator lamps, general sign lamps, etc.
Note that the foregoing embodiments have dealt with the cases where
the projection lenses 12 and 23 have flat rear surfaces. This is
not restrictive, however, and it is understood that the rear
surfaces may be formed in other shapes, such as a concave shape so
as to surround the light sources (such as the bulb 11 and the
LED).
As has been described, the exit surface of the projection lens can
have a distribution control characteristic. The light incident on
the projection lens from the light source or the reflecting surface
is thus focused and controlled in light distribution by the
projection lens. This can eliminate the need for distribution
control members that are separate from the projection lens, thereby
reducing the light transmission loss in the optical system. The
entire lighting device can also be configured compactly with a
lighter weight. In addition, the rim of the projection lens, as
viewed from the front, is not necessarily perfectly circular, but
can be differently shaped, including rotationally asymmetric in
shape. This allows for innovative designs for enhanced
merchantability and novelty.
As described above, it is possible to provide a lighting device of
simple configuration which can be formed compactly in the direction
of the optical axis and which can have a reduced weight on the
whole. The lighting device can also have a functional,
three-dimensional innovative appearance for enhanced
merchantability and novelty.
While there has been described what are at present considered to be
beneficial and exemplary embodiments of the invention, it will be
understood that various modifications may be made thereto, and it
is intended that the appended claims cover all such modifications
as fall within the true spirit and scope of the invention.
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